1. Field of the Invention
The present invention relates to a current sensor, and particularly relates to a current sensor having a signal line from which a detected signal is transmitted to the outside.
2. Description of the Related Art
A current sensor that measures a current flowing through a bus bar (a measured current path) is used in order to control or monitor various electric apparatuses. As such a current sensor, a sensor is known which includes a magnetic sensor element that detects a magnetic field generated around a current. Japanese Unexamined Patent Application Publication No. 2012-122793 discloses a current sensor including a Hall element as a magnetic sensor element.
FIG. 8 is a perspective view of a current sensor of the related art described in Japanese Unexamined Patent Application Publication No. 2012-122793. As shown in FIG. 8, the current sensor 110 of the related art includes a long plate-shaped bus bar 111 composed of a conductor, a core 112 surrounding the bus bar 111, and a Hall IC (Integrated Circuit) 113.
In the current sensor 110 of the related art, the Hall IC 113 is configured to house a Hall element and an IC in one package and is able to detect a magnetic flux passing through a magnetosensitive surface 113a of the Hall IC 113. As shown in FIG. 8, a gap 112a is provided in the core 112, and the Hall IC 113 is inserted in the gap 112a and disposed on the bus bar 111.
When a measured current flows through the bus bar 111, a magnetic field is generated around the bus bar 111 to form a magnetic path in the core 112. The gap 112a is provided so as to be orthogonal to the magnetic path, and a magnetic flux passing along the magnetic path passes through the magnetosensitive surface 113a of the Hall IC 113. Thus, it is possible to detect the current flowing through the bus bar 111. In addition, as shown in FIG. 8, a plurality of terminals 120a to 120d are provided to the Hall IC 113. A plurality of terminals or signal lines are connected to the plurality of terminals 120a to 120d, and an output signal of the Hall IC 113 is transmitted to the outside therethrough.
However, the plurality of terminals 120a to 120d extend parallel to the bus bar 111 and in a direction parallel to the magnetosensitive surface 113a. Thus, capacitances are formed between the plurality of terminals 120a to 120d and the bus bar 111 so that the plurality of terminals 120a to 120d and the bus bar 111 are capacitively coupled to each other.
Therefore, when a voltage applied to the bus bar 111 varies, a signal transmitted through the plurality of terminals 120a to 120d to the outside change to generate an output error. In addition, in the case where signal lines or the like (not shown) are connected to the plurality of terminals 120a to 120d, capacitive coupling occurs between the bus bar 111 and the signal lines or the like, and entire capacitive coupling with the plurality of terminals 120a to 120d and the signal lines or the like is increased. Thus, change in an output signal easily occurs due to voltage variation in the bus bar 111.
Furthermore, the plurality of terminals 120a to 120d and the signal lines or the like are disposed near the bus bar 111. Thus, electromagnetic noise generated by a current flowing through the bus bar 111 is superimposed on the plurality of terminals 120a to 120d and the signal lines or the like, and an output error is increased.